Thread: questions about laminated pine panels

Originally Posted by kingy82

I am embarking on a project to build my son a shelving unit using the panels bought at the local megastore 1800 x 450 x 19

im planning on screwing together, my questions are as follows if anyone can help.

1) is screwing into edge 19mm a good option?
2) after aclimatising the timber onsite ( i noticed the front panel was warped in store), should i paint all surfaces at least with a undercoat before screwing together?
3) is gluing and screwing a good option?

on a completely seperate note, does someone have a detail or a link to some over window awning designs (triangular, that utilise pine or hardwood and are easily constructed by a relative novice?)

thanks in advance

Bit of a novice myself in here, so if anyone wants to chime in and overrule me, please feel free, but in my limited experience:

1: Screwing into 19mm is fine. Just make sure you pre-drill to the 'core' size of your screw (so that you're letting the thread engage the timber and not forcing the fibres apart by trying to jam the solid shank through it) and don't use 'too thick' a screw - make sure you have plenty of wood left behind to support it. And just for reference, you should also be pre-drilling your 'outer' piece (the one you're screwing "through" as opposed to "into") to a diameter that lets the screw thread pass through it unimpeded. The idea of a screw is that it 'bites' into the back piece and pull it in towards its head, sandwiching whatever is in-between - those should be able to 'float' and not be dragged along with the thread, meaning there's no pressure being applied between it and anything else that's also "riding" the thread - ie the other piece of timber..

2: If you're ONLY screwing it together, sure, why not. However if you're gluing it up (highly advisable), then any finish on the timber will interfere with the glue and should be avoided. If you absolutely must pre-finish, mask off any areas with a non-permeable tape beforehand so you can still have a raw surface for the glue to work on.

3: most modern glues (and even most older ones, for that matter) are generally stronger than the wood you're joining. Failures at glue joints are generally from the timber shearing away, not the glue 'breaking'. As strange as it might seem, screws don't really add much strength to that, and if used incorrectly (eg by NOT pre-drilling), can actually wind up weakening or splitting your wood. Think of them as 'internal clamps' to hold pieces together while your glue dries. If you want your finished product to be able to be taken apart, you can use screws alone to create a joint which can be separated at a later date.. but be aware that (particularly in a soft wood like pine) it may not be particularly strong.

Originally Posted by MicN

3: most modern glues (and even most older ones, for that matter) are generally stronger than the wood you're joining. Failures at glue joints are generally from the timber shearing away, not the glue 'breaking'. As strange as it might seem, screws don't really add much strength to that, and if used incorrectly (eg by NOT pre-drilling), can actually wind up weakening or splitting your wood. Think of them as 'internal clamps' to hold pieces together while your glue dries. If you want your finished product to be able to be taken apart, you can use screws alone to create a joint which can be separated at a later date.. but be aware that (particularly in a soft wood like pine) it may not be particularly strong.

Hi Guys,

That's true however you need to consider that gluing endgrain will not result in a strong joint. You can achieve very strong bonds using long grain joints however.

I have some experience with the type of panel you're talking about. I built some shelves/bookcase out of it a while back. I only used glue on all the joints however i did have a backing panel of 6mm MDF which sat in dado grooves cut into the pine panel, this added the lateral strength that would otherwise be missing with glue only joints. I should note though that as I was using those shelves for more and more book storage (heavy) I went back and added screws to the joints to provide a backup strength in case any of the glue failed (as its on endgrain to long grain joints).

So if you can, definitely use the glue and screw method. Another option which may be useful also is to use through dowels. You just create the joints using glue only and then when it's all dry you can drill some holes, plug them with glued dowels and then when the glue dries again you can flush cut the dowels and plane them back til the surface is smooth. This approach tends to look nicer than screws also.

Good luck.
Mat

These ones I just made up from 100 x 50 uprights, 70 x 35 outriggers cut at 60 degrees and the slats were 70 x 16 fence palings.

Cheers
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